Page 1
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
Servo Press TechnologyApplications for Today and Tomorrow
Eren Billur and Taylan AltanCenter for Precision Forming
The Ohio State University www.cpforming.org & www.ercnsm.org
August 23, 2012
Page 2
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
2
Servo-Drive Presses- Outline
• Introduction• Servo-Drive Characteristics• Servo-Drive Press Mechanisms• Applications• Die Cushions• Summary/ Future Outlook
Page 3
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
3
(4) Other Process at BDC(Multi Process)
(4) Other Process at BDC(Multi Process)
(5) Prevention of noise and shock at contact or breakaway of tools
(5) Prevention of noise and shock at contact or breakaway of tools
(6) Synchronize withfeeder
(6) Synchronize withfeeder
Crank or Link pressFixed Motion
Time
Sli
de
Po
sit
ion
Cycle time of mechanical pressCrank or Link press
Fixed Motion
Time
Sli
de
Po
sit
ion
Cycle time of mechanical press
(2) Best speedfor materials
(2) Best speedfor materials
For
min
g le
ngth
(2) Best speedfor materials
(2) Best speedfor materials
For
min
g le
ngth
(3) Improve accuracy bydwelling at BDC
(3) Improve accuracy bydwelling at BDC
Standstill at BDC
(3) Improve accuracy bydwelling at BDC
(3) Improve accuracy bydwelling at BDC
Standstill at BDC
(1) Variablestrokelength
(1) Variablestrokelength M
inim
um
str
oke
leng
th
(1) Variablestrokelength
(1) Variablestrokelength M
inim
um
str
oke
leng
thCycle time of
Free motion press
Free motion press
Cycle time of Free motion press
Cycle time of Free motion press
Free motion press
The flexibility of slide motion in servo drive (or free motion) presses. [Miyoshi, 2004]
Servo-Drive Characteristics
Page 4
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
4
Servo-Drive Characteristics
• Precise ram position and velocity control, anywhere in stroke-easier set up
• Adjustable stroke length (TDC and BDC)• Ram position/ velocity can be synchronized with
automatic part transfer• In deep drawing, cycle times can be shorter than in
mechanical presses• Considerable savings in energy• Dwell at BDC/ restriking/ vibrating and variable blank
holder force (BHF)• Max. motor torque available during the entire stroke
Page 5
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
5
Servo-Drive Mechanisms
• Low Torque/ High RPM Motors Use Ball Screws or/and Linkage Mechanisms
• High Torque/ Low RPM Motors Use Existing Crank and/or Link Press Drives
Page 6
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
6
High RPM/ Low TorqueMotor Drive 1/2
Servo Motor
Ball Screw
Slide
Bolster
Linear sensor
Timing belt
Schematic of servo press with high speed-low torque servo-motors with belt and ball screw drive. [Miyoshi, 2004]
Page 7
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
7
Schematic of servo press with high speed-low torque servo-motors with linkage drive. [Miyoshi, 2004]
Servo Motor
Slide
Eccentricload
Right / Left independent control
Linearsensors
Servo Motor
Linearsensors
Slide
Eccentricload
Right / Left independent control
Linearsensors
Servo Motor
Linearsensors
High RPM/ Low TorqueMotor Drive 2/2
Page 8
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
a) C-Frame Servo Press (Aida)
Power Source Balancer tank Main gear
Servomotor
Capacitor
Drive Shaft
8
Low RPM/ High TorqueMotor Drive 1/2
b) Stroke-Time program for warm forming of Al and Mg sheet
Page 9
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFLow RPM/ High TorqueMotor Drive 2/2
9
Servo-Press Drive Using Conventional Crank Mechanism Courtesy- Aida
Page 10
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFHybrid Servo Press
Block diagram of a hybrid servo press (ABB)10
Page 11
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFHybrid Servo Press
Simplified 3D-view of a hybrid servo press, seen from above (ABB)
11
Page 12
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
12
Modern Stamping Lines UsingLarge Servo-Drive Presses
• BMW- Leipzig & Regensburg (Germany) – SCHULER 2009 - 2500 ton servo-drive drawing press - 17 SPM
• BMW – Leipzig, Regensburg and Shenyang (China) – SCHULER – 2012 – 7 tandem lines on order.
• HONDA - Suzuka (Japan) – AIDA 2009 – 2500 ton tandem line – 18 SPM
• Kamtek/COSMA – AIDA 2011 - 3,000 ton, 30 strokes/min• Honda-America – Ohio and Alabama - AIDA 2012 - 2,500
ton tandem lines• Hyundai – Korea – ROTEM 2012 – 1000 ton Tandem line• Others ?
Page 13
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
Improved Formability
Improved Productivity Energy-Saving
・ System with optimized press forming requirements for each product
・ Press-to-Press Loading Motion: System is optimized for each product.
・ Die cushions have an energy regeneration system
13
Schematic of Servo-press tandem line (Aida/Honda)2500 ton/ 18 SPM (2009)
Page 14
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
14
Servo-press tandem line (Schuler/BMW)2500 ton/ 17 SPM (2009)
One drawing press + 5 presses for follow-up operations
Source:BMWarchive.de
Technical Data:
Total press force: 10,300 tons
Drawing press force: 2,500 tons
Total length of press line: 98 meters
Length o press: 34 meters
Strokes per minute: 17
Source:Schulergroup.com
Page 15
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
15
Servo Tandem Line at Suzuka (Japan) Plant(Honda)
Page 16
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
16
Comparison between the slide motions of an 1100 mechanical and servo drive press for identical slide velocity during forming [Bloom, 2008].
Applications- Deep Drawing 1/3(Courtesy- Schuler)
Page 17
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
17
Decrease in cycle time by reducing the stroke length and operating the servo press in “pendular” mode (progressive die stamping, 200% increase in output) [Bloom, 2008]
Applications- Deep Drawing 2/3(Courtesy- Schuler)
Page 18
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
18
Decrease in cycle time as well as in impact speed using a servo press (150% increase in output) [Bloom, 2008]
Applications- Deep Drawing 3/3(Courtesy- Schuler)
Page 19
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
19
Side Panel Outer Deep Drawing Case Example (Honda)
Page 20
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
20
Applications- Blanking/ Ironing
Slide motion used for partial and finish blanking [Miyoshi, 2004 / Komatsu]
Precision Formed Part a) partially blanked, b) finished blanked [Miyoshi, 2004 / Komatsu]
Page 21
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
Item : Eye glass frameMaterial : Titanium based Shape-memory Alloy
By multiple step motion,Three processes turnedinto single process.
Three processes had been required to control the springback.
Multiple step motion
21
Applications- Reduction of Springback(Courtesy- Komatsu/ Hamamoto)
Page 22
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
IT IS POSSIBLE TO DIGITALLY SET THE OPTIMAL WORKING SPEED, THEREBY INCREASING DIE LIFE.
SUS304
PIERCING A HOLE WITH A SMALLER DIAMETER THAN THE MATERIAL THICKNESS (INCLINED HOLE PIERCING)
Al STEPPED HOLE PIERCING(80% BURNISHED SHEAR FACE)
22
Applications- Blanking/ Ironing Courtesy – Aida)
Page 23
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
SINCE THE PRESS CAN BE RUN AT LOW SPEEDS, IT IS NOT NECESSARY TO SWITCH TO A LARGER CLASS PRESS TO FORM HARD-TO-DRAW MATERIAL.
WRINKLES CAN OCCUR WHEN THERE IS INSUFFICIENT PRESS RIGIDITY AND THE DRAWING SPEEDS ARE NOT OPTIMIZED.
DRAW WRINKLES CAN BE AVOIDED BY SLOWING DOWN THE DRAWING SPEED. (SINCE WORKING ENERGY IS ALWAYS AVAILABLE, THE PRESS DOES NOT STOP EVEN AT INCHING SPEEDS.) 23
Applications- Blanking/ Ironing (Courtesy – Aida)
Page 24
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
IT IS POSSIBLE TO SET THE OPTIMAL FORMING MOTION AND TIMING FOR SECONDARY PROCESSES.
(STAKING AND ASSEMBLY)
ASSEMBLY OPERATION OF A SQUARE NUT (M5) IN A BRACKET DURING A PROGRESSIVE FORMING OPERATION
STAKING A PIN ( 3.6) IN A CHASSIS ∅DURING A PROGRESSIVE FORMING OPERATION
24
Applications- Auxiliary Operations (Courtesy – Aida)
Page 25
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
Tool and process design guidelines to improve formability
Aida Servo Press (used in warm forming of Al, Mg and Ti sheet)
Power Source Balancer tank Main gear
Servomotor
Capacitor
Drive Shaft
25
Applications- Warm Forming of Al, Ti, Mg, and SS
Page 26
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
AL 5754- O
T (oC) LDR
RT 2.1
250 2.5
300 2.9
T (oC) LDR
RT 2.1
275 2.5
275 2.9
AL 5052-H32
Preliminary results (Velocity range : 2.5-50mm/sec)
Note : RT: Room temperature, LDR : Limit draw ratio
Cup Diameter : 40mm26
Applications- Warm Forming of Al
Page 27
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
T (oC) LDR
RT -
275 2.6
275 3.2
Mg AZ31-O
Preliminary results (Velocity range : 5-50mm/sec)
Note : RT: Room temperature, LDR : Limit draw ratio
Cup Diameter: 40mm
T (oC) LDR
310 2.5
Ti (Grade 1)
27
Applications- Warm Forming of Mg and Ti
Page 28
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
28
Press slide motion used in warm forming processes (TDC - Top Dead Center, BDC – Bottom Dead Center)
Warm formed lap top case from Mg alloy(Courtesy – AIDA)
Applications- Warm Forming of Mg Lap Top Case
Page 29
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
Die
Cus
hion
For
ce (
kN)
29Elimination of Pressure Surge in the Die Cushion
Servo-Hydraulic Cushion (Courtesy-Aida)
Page 30
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFCapabilities of the Self-Driven Hydraulic Servo Cushion
• pre-acceleration to reduce the impact speed between the die and blank holder
• variable pressure / force capability to control blank holder force/pressure during stroke
• prevention of momentary return of the cushion after BDC to avoid pressure on the top of the part
Page 31
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPF
SMS/M
PowerDirection
Closed Hydraulic Circuit
Power Regeneration: Approx. 70%
Pump Rotation Direction
Motor Torque Direction
Pressure Sensor
Linear Scale
31
Servo-Hydraulic Cushion (Courtesy-Aida)
During Down Stroke, Cushion Pressure Generates Power
Page 32
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFAdvantages of Servo- Press Technology- Applications in Forming AHSS -
1. Major Challenges in Forming AHSS (DP, TRIP, TWIP) include:
• lower formability (ductility) and higher probability of fracture• variations in mechanical properties form batch to batch• higher forming forces and high sheet/die interface pressures &
temperatures• Excessive tool wear, rapid increase in down-force and large
reverse tonnage• large springback due to large tensile strength
32
Page 33
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFAdvantages of Servo- Press Technology- Applications in Forming AHSS -
2. Precise Ram Position (including dwell) and velocity control
• allows for easier die set-up• prevents noise and shock when the ram is contacting the
workpiece (hydraulic cushion with pre-acceleration)• improves formability and reduces fracture by reducing ram
velocity during deformation (drawing, stretching and bending), improves die/sheet lubrication by reducing temperature increase at sheet/die interface
• reduces shock loading and reverse tonnage in blanking, improves tool life
33
Page 34
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFAdvantages of Servo- Press Technology- Applications in Forming AHSS -
3. Dwell at BDC and Pendulum Motion allows:
• dwell at BDC and restriking quickly through pendulum motion before the formed material fully strain hardens, reduces springback (die design is still very important)
4. Adjustable Stroke Length (TDC to BDC):
• provides flexibility so that in the same press, drawing, blanking and coining can be conducted with maximum productivity (high strokes/min)
34
Page 35
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFAdvantages of Servo- Press Technology- Applications in Forming AHSS -
5. Ram Position/Velocity can be:
• synchronized with automatic (or robotic) part transfer to increase strokes/min
• adjusted to maximize strokes/min while maintaining lower ram velocity during forming stage
35
Page 36
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFServo-Drive Press TechnologySummary / Outlook
• Gap presses up to 150 ton are in production (15+ years)• Straight Side stamping presses up to 3000 ton are already
built• Direct drive (high torque) motors and energy recovering
cushions are used• High speed automotive stamping transfer presses (18
strokes/min)/ Schuler-BMW/ Aida-Honda and Cosma / Komatsu-Toyota & others
• Novel tool design techniques for servo drive technology are being developed
• Servo-drive presses will greatly contribute to improving the technology for forming AHSS and Al alloys
36
Page 37
© Copyright Engineering Research Center for Net Shape Manufacturing, 2012Stamping Group
CPFCPFQuestions/Comments
Taylan Altan, Professor and Director
Center for Precision Forming (CPF)
www.cpforming.org / www.ercnsm.org
The Ohio State University, Columbus, OH
Email: [email protected] , Ph: (614) 292 5063
Source: Chapter 11 – Electro-mechanical
Servo-Drive Presses in “Sheet Metal Forming, Fundamentals”,
Vol. 1, by Altan/Tekkaya, ASM International, www.asminternational.org
37